Capsaicin was applied to the exposed radial nerve of adult flying foxes (n = 5) and cats (n = 2) while recording in primary somatosensory cortex froma single neuron with a receptive field on digits 1 or 2. Within four minutes of application of capsaicin the borders of these receptive fields dramatically expanded. In a further four flying foxes it was shown, with subcutaneous delivery just proximal to the receptive fields, that capsaicin need affect only afferents from the region of a neuron's receptive field to induce expansion. Capsaicin applied directly to a nerve, or subcutaneously in high concentrations, is a selective neurotoxin that rapidly prevents the propagation of action potentials in most C-fibres. The result provides a partial explanation for experiments involving the specific and complete denervation of receptive fields of neurons in primary somatosensory cortex. Such denervation does not lead to unresponsiveness but to immediate sensitivity to stimulation of areas surrounding the original fields. Thus it appears that some subclass of capsaicin-sensitive C-fibres provides a primary source for the masking inhibition that normally limits the extent of the receptive fields of cortical neurons.

Item Type:	Refereed Article
Keywords:	capsaicin; animal experiment; article; bat; cat; controlled study; drug therapy; evoked somatosensory response; priority journal; radial nerve; Afferent Pathways; Animals; Capsaicin; Cats; Denervation; Foxes; Nerve Fibers; Neurons
Research Division:	Biomedical and Clinical Sciences
Research Group:	Neurosciences
Research Field:	Neurology and neuromuscular diseases
Objective Division:	Health
Objective Group:	Clinical health
Objective Field:	Clinical health not elsewhere classified
UTAS Author:	Calford, MB (Professor Mike Calford)
ID Code:	91267
Year Published:	1991
Web of Science® Times Cited:	101
Deposited By:	Research Division
Deposited On:	2014-05-13
Last Modified:	2014-05-13
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